in Lambda/Layer/crypto/python/lib/python3.8/site-packages/pycparser/ply/yacc.py [0:0]
def compute_lookback_includes(self, C, trans, nullable):
lookdict = {} # Dictionary of lookback relations
includedict = {} # Dictionary of include relations
# Make a dictionary of non-terminal transitions
dtrans = {}
for t in trans:
dtrans[t] = 1
# Loop over all transitions and compute lookbacks and includes
for state, N in trans:
lookb = []
includes = []
for p in C[state]:
if p.name != N:
continue
# Okay, we have a name match. We now follow the production all the way
# through the state machine until we get the . on the right hand side
lr_index = p.lr_index
j = state
while lr_index < p.len - 1:
lr_index = lr_index + 1
t = p.prod[lr_index]
# Check to see if this symbol and state are a non-terminal transition
if (j, t) in dtrans:
# Yes. Okay, there is some chance that this is an includes relation
# the only way to know for certain is whether the rest of the
# production derives empty
li = lr_index + 1
while li < p.len:
if p.prod[li] in self.grammar.Terminals:
break # No forget it
if p.prod[li] not in nullable:
break
li = li + 1
else:
# Appears to be a relation between (j,t) and (state,N)
includes.append((j, t))
g = self.lr0_goto(C[j], t) # Go to next set
j = self.lr0_cidhash.get(id(g), -1) # Go to next state
# When we get here, j is the final state, now we have to locate the production
for r in C[j]:
if r.name != p.name:
continue
if r.len != p.len:
continue
i = 0
# This look is comparing a production ". A B C" with "A B C ."
while i < r.lr_index:
if r.prod[i] != p.prod[i+1]:
break
i = i + 1
else:
lookb.append((j, r))
for i in includes:
if i not in includedict:
includedict[i] = []
includedict[i].append((state, N))
lookdict[(state, N)] = lookb
return lookdict, includedict